You’ve drawn up your retatrutide and now you’re standing there with the syringe, not totally sure where it’s supposed to go. Short version: into the fat just under your skin. Most people use the stomach, thigh, or back of the arm. Here’s where each spot is and how to rotate so you’re not hitting the same place every week.
The Bottom Line
Retatrutide is injected subcutaneously. The four reliable sites are abdomen (left/right of the navel), upper thigh (front/outer), upper outer glute, and upper arm. Volumes are small (0.05-0.25 mL at typical microdose concentrations), so a 29-31G, 5/16” insulin syringe is the standard. Rotate every injection, even on a weekly cadence.
Retatrutide-specific injection guidance: which sites actually work, what makes reta different from semaglutide and tirzepatide site-wise, and a rotation pattern you can stick with on a weekly cadence.
If you want the full primer on SubQ vs IM and all seven subcutaneous sites in detail, our broader peptide injection sites guide covers that. This page sticks to what’s specific about retatrutide.
Best Retatrutide Injection Sites
Retatrutide goes subcutaneously, into the fat just under the skin, not into muscle. The four reliable sites:
L. AbdomenR. AbdomenL. ThighR. ThighR. Upper ArmL. Upper Arm
L. GluteR. Glute- Abdomen - the default. Stay at least 2 inches from the navel, skip the midline, avoid visible veins. Easy to reach, consistent absorption, and most people have enough fat here even when lean.
- Upper thigh (front/outer) - middle third between knee and hip. Pinch a fold; if you can grab tissue, it works. Skip the inner thigh - more nerve endings, more sting.
- Upper outer glute - upper-outer quadrant of the buttock, above the sit bone. Often the most comfortable site (fewer nerve endings than the abdomen). Use a mirror or inject standing.
- Upper arm (back/tricep) - viable if you have enough fat to pinch, but hardest to self-inject. Many weekly injectors skip arms entirely and that’s fine.
The Bottom Line
Reta-specific note: because injection volumes are tiny (often 5-25 units on an insulin syringe), site choice rarely affects dose accuracy. It affects tissue health. Pick sites you can hit cleanly and rotate them.
Injection Technique
Standard subcutaneous technique applies. Three steps:
Proper subcutaneous technique: pinch & lift a skin fold, insert at 45°, inject slowly over 5–10 seconds.
Use a 29-31 gauge, 5/16 inch (8mm) insulin syringe. At typical microdose concentrations (2-4 mg/mL), a weekly 1 mg dose lands at 0.25-0.5 mL - well within an insulin syringe’s accuracy range. For a deeper walkthrough on reading the syringe markings, see our insulin syringe guide. For the unit count itself, run your vial through the retatrutide reconstitution calculator.
Rotation Pattern for Weekly Retatrutide
Most retatrutide protocols are once-weekly. That sounds infrequent enough that rotation shouldn’t matter - but it does. Injecting the same square inch every Sunday for six months is more than enough to develop lipohypertrophy, and the resulting unpredictable absorption is one of the underdiagnosed causes of “my dose stopped working.”
A simple 4-week rotation:
| Week | Site |
|---|---|
| 1 | Left abdomen |
| 2 | Right thigh |
| 3 | Right abdomen |
| 4 | Left thigh |
| 5+ | Repeat, micro-shifting 1-2 inches within each site |
Add glutes if you want a 6-week cycle. Track which site you used each week - it’s the only way to stay honest about rotation, since memory is unreliable across months.
How Retatrutide Differs from Semaglutide and Tirzepatide
Site mechanics are identical - all three are SubQ, all three absorb at similar rates across abdomen/thigh/arm/glute. What’s different:
- Injection site reactions are slightly more common with reta than with tirz in Phase 2 data - mild redness, itching, transient swelling. Aggressive rotation matters more here than on tirz.
- Volumes are usually smaller. Microdosed reta often runs 0.05-0.25 mL per shot versus 0.25-0.5 mL for branded tirz pens. An insulin syringe is the right tool.
- Weekly cadence is the standard. Some users split into twice-weekly to smooth side effects. If you split, treat each shot as its own rotation step (so 8-site rotation instead of 4).
When to Skip a Site
- Bruising or lingering tenderness from a previous injection
- Any visible lump, hardness, or dimpling (early lipohypertrophy)
- Active rash, broken skin, or recent shaving nicks
- Tattoos, moles, or scars (move at least 1 inch away)
If a site stays sore for more than 48 hours after injection, give that whole region (not just the exact spot) a 4-6 week rest.
Frequently Asked Questions
Where do you inject retatrutide?
Retatrutide is injected subcutaneously into the abdomen (at least 2 inches from the navel), the front or outer upper thigh, or the upper outer glute. Upper arms work for people with enough subcutaneous fat there. All four sites absorb at roughly the same rate, so rotation is about tissue health, not dose response.
Is retatrutide subcutaneous or intramuscular?
Subcutaneous (SubQ). The Phase 2 and Phase 3 trial protocols, and every community microdosing protocol we’ve seen, use SubQ. There is no published or community use case for IM retatrutide, and the small injection volume makes SubQ the obvious route.
How often should you rotate retatrutide injection sites?
Rotate every injection. Even on a weekly schedule, returning to the exact same spot week after week is enough to develop lipohypertrophy over a few months. A simple 4-site rotation (left abdomen, right thigh, right abdomen, left thigh) gives each spot ~4 weeks to recover.
Can injection site choice affect retatrutide side effects?
Site choice doesn’t meaningfully change GI side effect intensity, since absorption rates are similar across SubQ sites. But injecting into damaged tissue (lipohypertrophy) absorbs unpredictably and can produce more erratic side effects week to week. Site rotation is more about consistency than reducing nausea.
What needle size is best for retatrutide?
Most people use a 29-31 gauge, 5/16 inch (8mm) insulin syringe. Retatrutide injection volumes are small (often 0.05-0.25 mL at typical microdose concentrations), so an insulin syringe gives the most accurate measurement and least painful injection.
Related Reading
- Peptide injection sites: SubQ vs IM, the full primer
- Retatrutide dosing guide
- Retatrutide reconstitution calculator and guide
- Microdosing retatrutide: what lean users actually run
- Retatrutide side effects guide
This article is for educational purposes only and is not medical advice. Talk to a licensed clinician before starting, changing, or stopping any medication.
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